Inhibited oil



Patented F b. 15, 1 944 UNITED STATES PATENT OFFICE Stanley P.

Waugh, Westfield, N. 3., assignor to Tide Water Associated Oil Company,New York, N. Y., a corporation of Delaware No Drawing. Application April18', 1941, Serial No. 389,169

21 Claims.

prevail and a thin film of oil is in contact with hot meta1 surfaces, asin the lubrication of internal combustion engines, or where the oil isused in oxidizing atmospheres or at elevated temperatures, as intransformers, in cable wrapping and metal cutting operations the oil maytend to deteriorate.

Another factor which influences the value and service life oflubricants, especially oils used for the lubrication of internalcombustion engines, is the degree of corrosive effect which the oilsexert upon the bearing surfaces in the engine. Engine bearings ofcadmium-silver, cadmium-nickel or copper-lead alloys are now frequentlyused instead of the more conventional Babbitt metal bearings. Experiencewith bearings of the character of cadmium-silver, cadmium-nickel, andcopper-lead has proved that they are extremely susceptible to rapiddeterioration in service when lubricated with many available lubricatingoils, particularly lubricating oils considered by conventional criteriaas being superior in other respects.

Mineral oils are improved as respects deterioration characteristics byrefining methods which remove or convert, at least in part, certaindeterioration constituents normally present therein. @efining withchemicals, as with selective solvents of the character of phenol, liquidsulfur dioxide, nitro-benzene, iurfural, and others, by clay filtrationor by treatment with sulfuric acid, is often resorted to. The refinedproducts, however, still are susceptible to oxidation, polymerization orother change to which may be attributed impairment of the oil asindicated by acid and sludge formation, color degradation,-. inordinateviscosity increase or tendency to cause corrosion of the above statedalloy bearings. Conditions often observed in internal combustion enginesafter long running at sustained high speeds,

by the conditions ob---, taining during use. Where high temperaturessuch as stuck piston rings, clogged ring grooves and oil holes andgeneral deposition of "varnish". on the various parts of the motor,particularly when many or the lower viscosity motor lubricating oils areemployed as the lubricating medium, have been attributed todeterioration of the oil.

It is an object of the present invention to retard or inhibit thedeterioration of mineral oils. Another object is to retard or inhibitthe corrosive deterioration of cadmium-silver, cadmiumnickel,copper-lead or like bearings by refined mineral lubricating oils.

A further object is to provide effective inhibitors for lubricating orlike oils of petroleum ori- A more specific object is-to provide minerallubricating oils containing in amounts eflfectlve to retard or inhibitdeterioration of said oils and corrosion of cadmium-silver and likebearing alloys, salts of esters of sulphocarboxylic acids. Anotherobject is to provide engine lubricating oils having satisfactorylubricating properties and low vamish depositing characteristics at highoil temperatures and sustained engine speeds.

Other objects and advantages will appear from the following descriptionof the invention and I the illustrative examples.

Illustrative of inhibitors which may be used according to the presentinvention and one which has shown to be particularly effective is thecalcium salt of dioctyl ester of sulphosuccinic acid, otherwise known ascalcium dioctyl sulfo succinate. The high eiiectiveness of thissubstance when incorporated in small amounts in engine lubricating oilis demonstrated by the following tests.

The runs were made with an internal combustion engine lubricating oil of10 S. A. E. viscosity rating comprising a blend of solvent refinedPennsylvania neutral oil with a conventionally produced Pennsylvaniabright stock. This grade of oil has in many instances caused ineilicientengine operation and sometimes complete engine failure due to itstendency to cause varnish" deposits in service. The engine used for thetests was an overhead-valve six cylinder automobile engine. In each casethe engine was run at a substantially constant speed of 3150 R. P. M.(equivalent to miles per hour) under a load of 35 brake horsepower.During the runs the oil temperature was maintained at 280 F. and thewater jacket temperature at 200 F.

In the first test the engine which had been thoroughly cleaned insidewas run for an equivalent of 2500 miles under the stated conditionsusing as the lubricating oil the uninhibited Pennsylvania S. A. E. oildescribed above. At the end of this run the oil was drained and themotor disassembled for inspection. Largeamounts of vamish-like materialwere found deposited on the inside walls of .the engine, piston skirts.crankshafts and other moving parts. The oil screen was partially blockedwith deposited sludge and the ring slots and oil holes in the pistonswere partially blocked with solid material.

The engine was then thoroughly cleaned of deposited material andre-assembled. In the next run a resh supply of the same S. A. E. 10 oilto whic 1.0% by weight of the calcium salt oi dioctyl ester ofsulphosuccinic acid had been added was used. The engine was run underthe same conditions as in the first run except that it was stopped anddisassembled after an equivalent of 3000 miles instead of 2500 miles.The effect of the small amount of inhibitor was apparent from aninspection of the inside of the motor. The inner walls of the motor andthe crankshaft were substantially clean and free from solid deposit.Only a very thin layer of varnish had deposited on portions of thepiston skirt. Only a small amount of sludge appeared on the coverplates. The oil pump screen was clean and unblocked, and the ring slotsand oil drain holes were clean and unblocked. The motor, after this runwith inhibited oil was characterized by its generally clean condition ascompared with its condition after the first run using uninhibited oil.

The presence of certain polar groups in the molecule of compounds ofthis invention is im portant. The polar carbonyl group, and particularlythe sulfonate polar group, appears to impart film strength and otherdesirable film characteristics, such as aiding in the formation of astrongly adsorbed protective film upon the hearing surfaces and othercorrodible parts. Free acid radicles are in general to be avoided,particularly when the oil is to be used in motors equipped with alloybearings, since a free acid would tend to promote corrosion.

Many compounds containing sulfonate groups, however, are notsufllcientlysoluble in oil and thus cannot be used as inhibitors. The compounds ofthis invention which contain the ester linkages in addition to thesulfonate group are soluble. Further, I have found that salts of thestated sulfo esters which contain branched chain alkyl groups are moreoil soluble than those of unbranched chain structure. The branched chaincompounds are therefore preferred. Ex-

, amples of suitable branched chain compounds suitable for use in thisinvention are the salts of di-isoamyl, di-isooctyl and di-heptadecylesters of sulfo di-carboxylic acids. The salts of branched chain estersof sulfo monocarboxylic acids are likewise more suitable than theunbranched chain esters of the corresponding acids for the same reason.Since, however, more branched chains can be added by esterificatlon ofthe dicarboxylic acids than by esteriflcation of the monocarboxylicacids the dicarboxylic acid esters are preferred as being more oilsoluble.

Inhibitors within the contemplated scope and practice of the inventioninclude not only the salts of esters of sulfo-dicarboxylic acids inwhich the hydrogen of the carboxyl groups have been substituted by likealcohol radical residues as in the case of calcium diactyl succinate,but also include mixed esters in which said hydrogens 7 number of carbonatoms are substituted by dissimilar radicals. Likewise the invention isnot to be considered limited to use of the calcium salts of theseesters, since other alkaline earth salts, the alkali metal salts, aswell as other metal salts such for example as aluminum are suitable, aswill be shown hereinbelow. In general, any salt of the stated esterseffective as an inhibitor for mineral oils is contemplated as beingwithin the scope of the invention.

Examples of other esters which have been found to give good results asinhibitors according to this invention are the salts of lauryl, amyi andoctyl alcohol esters of the sulfodicarboxylic acids.

In most cases the presence of a fraction of one percent ofthe inhibitorin the mineral oil will produce the desired result. Although such smallpercentages are generally useful in the practice of the invention, itshould be understood that larger proportions of inhibitors may be usedas deemed desirable. Satisfactory results are generally obtained whenusing the inhibitors in maximum amounts of the order of 1% by weight inthe oil.

One outstanding characteristic of the described compounds is theirtendency to emulsify mixtures of oil and water. These compounds aretherefore generally not suitable for use in lubricating oils which inservice are contacted with water, such as in the lubrication ofturbines, where excessive and objectionable foaming may result fromemulsificationof the oil with water present. The problem of excessivefoaming and emulsiflcation is generally not encountered in thelubrication of internal combustion engines with oil containing theinhibitors of this invention due to the relatively small amounts ofwater present in the crankcase. In some instances, however, internalcombustion engines are operated under conditions conducive to theformation of larger amounts of water in the crankcase than are formed inordinary service. It is therefore preferred to use as the inhibitor thealkaline earth salts, or the metallic salts such as aluminum, of theesters stated. in lieu of the alkali metal salts, since the former areless water-soluble than the latter and have less tendency to causeformation of troublesome emulsions.

Likewise I have found it preferable to use as inhibitors in enginelubricating oils and the like the salts of those esters having residualalcohol radicals of a relatively low number of carbon atoms. I havefound that, in general, the lower in the residual alcohol tendencytoward foaming in service. Thus, for example, the compounds of thestated type which contain residual alcohol radicals of from about 5 tomcarbon atoms are preferred over those compounds containing residualalcohol radicals of more than 10 carbon atoms since the former show lesstendency to form emulsions and cause foaming in service than the latter.

The utility of my inhibitors when used in internal combustion enginelubricating oils in preradical, the less is the venting or retardingcorrosion of cadmium-silver" service conditions with the bearings ofcadmiumsilver and like alloys than exists in use of Babbitt bearing maybe a. factor involved in bearing corrosion. The presence of copper inthe form 45.9, viscosity at 100 F. 18.2, color 3.25. per cent carbonresidue 0.13, neutralization number 0.02.

The comparative results obtained appear in the following table:

Bearing Neut. munber Increase in Naphtba Carbon Gmvlty- 2 ,3???insolubles residue Per cent Per cent Per cent 1.24 26.7 7 8 24s 0.201.81 Nil 29.0 3 l 8. 7 1.05 Nil 24.2 0 7 2.2 0.24 0. 52 0.40 27. 3 A 130.85 1.55

of oil lines, etc., in the engine is also a factor, it

- supported in a chamber in which air is present,

and streams of the oil under test are continuously directed, under persq. inch pressure onto the sanded surfaces of bearing and strip for aperiod of 15 hours. The oil is maintained at a temperature of 325 F.Means are provided for recirculating the oil so that a .given quantityis used for a given test, thus simulating service conditions in anengine. The copper strip furnishes a reproducible and controlled sourceof catalyst. The apparatus described is the Underwood oxidation testingapparatus, supplied by the Scientific Instrument Company of Detroit,Michigan, and the test is carried out in this apparatus in accordancewith General Motors specifications.

The following results, obtained by utilization of the foregoing test forcomparativeevaluation of motor oils with and without the addedinhibitors of this invention, clearly evidence the effectiveness of theinhibitors in preventing bearing corrosion as well as deterioration ofthe oil. The oil used was a motor oil of S. A. E. rating comprising ablend of solvent refined Pennsylvania neutral oil with a conventionallyproduced bright stock. The oil had an A. P. I. gravity of 30.0; aviscosity at 210 F. of 54 Saybolt seconds, and 294 seconds at 100 F.;carbon residue of'0.40%, naphtha insolubles, nil; neutralization number0.02; flash point 445 F.; fire point 495 F.; pour point to 20 F.; color5. Before each run the test apparatus was carefully cleaned withsolvents to remove the deposited material from the previous run and thebearing and copper strip were each freshly sanded and weighed.

The results appear in the following table:

0 The above tests amply illustrate the effective- 15 ness of theinhibitors of this invention in preventing bearing corrosion anddeterioration of the oil.

The loss in weight of the cadmium-silver bearing used in the Underwoodtest is a measure of 20 the amount of corrosive products present ordeveloped in the oil being tested. Losses in weights of cadmium-nickel,copper-lead and the like bearings would be less under the same testconditions because the cadmium-silver alloy used is 25 more susceptibleto corrosion than the latter named'bearing metal alloys,

Neutralization number, although not a direct measure of corrosiveproperties, is an indication of the change taking place in the oilduring test and represents roughly the acidity of the oil.

40 hereinabove in detail in its application to motor lubricatingoils,-it should not be considered as limited to that field. For example,straight cutting oils, 1. e. oils used for heavy cutting operations onmetals (as distinguished from soluble" cutting oils), may be thusinhibited against deterioration in service. This type of oil is usuallycomposed of a blend of a mineral lubricating oil and sulfurizedvegetable oil such as sulfurized wood fatty acids. These oils areadapted to provide lubrication under extreme pressure conditions such asis often encountered in modern machine shop practice; but the oilsheretofore used tend to oxidize and polymerize to form gummy andresinous materials under the conditions prevailing in use, thusdecreasing their effectiveness for the intended purpose and shorteningthe useful service life of the oil.

According to this invention such cutting oils Table I 1 Bearing Neut.number Increase in i b.- aphtha Carbon 011 used lgorss in Gravity mg.Kgillilll gm. iszlizs itry insolubes residue Per cent Per cent Per centS. A. E. 20 (uninhibite .07 24.0 9. 6 44 0. 49 3.00 S. A. E. 20 plus0.5% of sodium dioctyl suite-succinct .01 29. 5 0.8 4 0.13 0. 90 S. A.E. 20 plus 0.5% of calcium dioctyl sulfo-succinate .01 29. 8 0. 4 6 0.04 0. 89 S A. E. 20 plus 0.5% of aluminum dioctyl sulfo succmete. Nil29. 9 0. 4 Nil 0. l6 0. 62

Further similar tests were made in the Underwood apparatus using aPennsylvania base motor oil of S. A. E. 10 rating consisting of a blendof 96% of solvent refined neutral oil and 4% bright stock having thefollowing characteristics: gravity 31.5, flash point 410 F., fire point465 F., pour point below minus 10 F., viscosity 210 F.

can be satisfactorily stabilized against deterioration in service byincorporating therein one or more of the inhibitors described above.Upon heating a cutting oil comprising about refined mineral oil andabout 10% sulfurized wood fatty acid base in metal container for 70hours 76 in an oven maintained between 220 and 230 F.

there resulted a large amount 01' hard adherent resin-like deposit uponthe surface of the metal container. When a fresh supp of the samecutting oil in which had been incorporated 1% 01' sodium dioctylsuiio-succinate was heated under identical conditions no resinous orgummy deposit was formed on the metal container and only a small amountof such deposit had occurred after 400 hours of heating. Thisaccelerated test clearly shows the efiectiveness of the addition agentsto this invention.

Summarizing, the invention comprises mineral oils having incorporatedtherein salts of esters of sulpho carboxylic acids in amounts efi'ectiveto inhibit deterioration of the oil in service, and is particularlyconcerned with providing viscous mineral lubricating oil of motor'grades containing such amounts of said compounds as to be inhibitedagainst deterioration and corrosive attack upon cadmium-silver,cadmiumnickel and copper-lead and like alloy bearings, and deposition ofvarnish and like material in service. The invention also naturallyincludes the method of lubricating engines and the like comprisingutilization of such inhibited 0115 as the lubricating medium.

I claim:

l. A substantially non-aqueous mineral oil composition not normallysusceptible to emulsiflcation in its intended uses comprising ahydrocarbon oil normally tending to deteriorate in service and a salt ofan ester of a sulfo carboxylic acid dissolved in said oil indeterioration inhibiting proportions.

2. A substantially non-aqueous mineral oil composition not normallysusceptible to emulsiflcation in its intended'uses comprising ahydrocarbon oil normally tending to deteriorate in service and a salt ofan ester of a sulfo dicarboxylic acid dissolved in said oil indeterioration inhibiting proportions.

3. A substantially non-aqueous mineral oil composition not normallysusceptible to emulsification in its intended uses comprising ahydrocarbon oil normally tending to deteriorate in service and a salt ofa dialkyl ester of a sulfo dicarboxylic acid incorporated in said oil indeterioration inhibiting proportions.

4. A substantially non-aqueous lubricant not normally susceptible toemulsification in its intended uses and useful in the lubrication ofinternal combustion engines comprising a hydrocarbon lubricating oil.ofmotor oil character normally tending in service to corrode alloys of thetype having substantially the corrosion susceptibility ofcadmium-silver, cadmium-nickel and copper-lead alloys and a salt of anester of a sulfo carboxylic acid incorporated with said oil in corrosioninhibiting proportions.

5. A substantially non-aqueous lubricant not normally susceptible toemulsification in its intended uses and useful in the lubrication ofinternal combustion engines comprising a hydrocarbon lubricating oil ofmotor oil character normally tending, in service, to deteriorate andhaving substantially the corrosion susceptibility of cadmium-silver.cadmium-nickel and copperlead alloys, and a salt of a dialkyl ester ofsuli'o succinic acid in proportions effective to inhibit said oildeterioration and alloy corrosion.

6. A substantially non-aqueous lubricant not normally susceptible toemulsification in its intended uses comprising a hydrocarbon 011normally tending to deteriorate in service and a salt of an ester of asulfo dicarboxylic acid in proporassaoarf tions eflective to inhibit orretard deterioratir of said 011, said salt containing at least one resilual alcohol radical or from about 5 to about 1 carbon atoms. I

7. A substantially non-aqueous mineral o composition not normallysusceptible to emuls flcation in its intended uses comprising a hydrrcarbon oil normally tending to deteriorate 1 service having incorporatedtherewith deteriorl tion inhibiting proportions of an alkaline cart saltof an. ester of a sulfo dicarboxylic acid.

8. A substantially non-aqueous mineral o composition not normallysusceptible to emulsi ilcation in its intended uses comprising a refinehydrocarbon oil normally tending to deteriorat in service havingdissolved in said 011 deteriora tlon inhibiting proportions of a dialkylsuccinat calcium sulionate. n V

9. A substantially non-aqueous mineral o1 composition not normallysusceptible to emulsi flcation in its intended uses comprising hydrocarbon oil normally tending to deteriorate 11 service having dissolvedtherein deterioration in hibiting proportions of dioctyl succinate calcium sulfonate. y 10. A substantially non-aqueous mineral oi compositionnot normally susceptible to emulsiflcation in its intended uses andsuitable for us as a cutting oil having extreme pressure characteristicscomprising a hydrocarbon oil and a salt of an ester of a sulfocarboxylic acid.

11. A substantially non-aqueous mineral oi composition not normallysusceptible to emulsiflcation in its intended uses and suitable for useas a cutting oil having extreme pressure characteristics comprisinghydrocarbon oil, sulfurized vegetable oil and deterioration inhibitingproportions of a salt of an ester of a sulfo dicarboxylic acid.

12. A substantially non-aqueous mineral oil composition not normallysusceptible to emulsiflcation in its intended uses comprisinghydrocarbon oil normally tending to deteriorate in service havingdissolved therein deterioration inhibiting proportions of a salt of anester of a sulfo dicarboxylic acid having branched chain structure.

13. A substantially non-aqueous mineral oil composition not normallysusceptible to emulsiflcation in its intended uses comprisinghydrocarbon oil normally tending to deteriorate in service havingdissolved therein deterioration inhibiting proportions of a salt of anester of a sulfo dicarboxylic acid having at least one residual alcoholradical of branched chain structure.

14. A substantially non-a ueous lubricant not normally susceptible toemu ification in its intended uses and useful in the lubrication 01'internal combustion engines comprising a hydrocarbon lubricating oil ofmotor oil character normally tending in service to deteriorate and causedeposition of solid material in-the engine, and a salt of a dialkylester of a sulfo dicarboxylic acid, said salt having branched chainstructure.

15. A substantially non-aqueous mineral oil composition not normallysusceptible to emulsification in its intended use comprising ahydrocarbon oil normally tending to deteriorate in service havingincorporated therein deterioration inhibiting proportions of a salt ofan ester of a sulfo carboxylic acid, said salt containing radicalstending to increase its solubility in said oil and being free from freeacid radicals.

16. An improved lubricating composition comprising a mineral oil anddissolved therein a small amount of an oil-soluble salt of calcium withan ester of a sulpho dicarboxylic acid of the general formula COOXwherein R is an aliphatic radical containing at least one sulphonicgroup and X and X1 are alcohol radicals containing at least five carbonatoms.

17. A compounded mineral lubricating oil containing a small amount of acalcium salt of a sulphonic acid dioctyl succinic ester.

18. A mineral oil composition comprising a hydrocarbon oil normallytending to cause ringsticklng and hearing corrosion in service, and asmall amount of an oil-soluble salt of an ester of a sulfo carboxylicacid efl'ective to inhibit such ring-sticking and bearing corrosion.

19. A mineral oil composition comprising a hydrocarbon oil normallytending to cause ringsticking and bearing corrosion in service, and asmall amount of an oil-soluble salt of an ester of a sulfo dicarboxylicacid effective to inhibit such ring-sticking and bearing corrosion.

20. A mineral oil composition comprising a hydrocarbon oil normallytending to cause ringsticking and bearing corrosion in service, and asmall amount of an oil-soluble salt of a polyvalent metal with an esterof a. sulfo carboxylic acid efl'ective to inhibit such ring-sticking andbearing corrosion.

21. A mineral oil composition comprising a hydrocarbon oil normallytending to cause ringsticking and bearing corrosion in service, and asmall amount of an oil-soluble aluminum salt of an ester of a sulfocarboxylic acid eilective to inhibit such ring-sticking and bearingcorrosion.

STANLEY P. WAUGH.

